1. Field of the Invention
The present invention relates generally to an optical sensor circuit for a semiconductor manufacturing device. More particularly, the invention relates to an optical sensor circuit that combines the functions of both “open-type” and “close-type” optical sensor circuits into a single optical sensor circuit.
A claim of priority is made to Korean Patent Application No. 10-2004-0110967 filed Dec. 23, 2004, the disclosure of which is hereby incorporated by reference in its entirety.
2. Discussion of Related Art
Optical sensors are commonly used to detect the positions and/or orientations of various components within a piece of semiconductor manufacturing equipment. For instance, optical sensors may be used to detect whether a printed circuit board is properly positioned or whether parts of the equipment such as doors, valves, and so forth, are properly positioned (e.g., open, closed, tilted, rotated, etc.). The optical sensors are generally coupled to or associated with actuators such as pivot motors, door motors, and air springs, which are used to adjust the positions and/or orientations of the various components.
An ion-implantation apparatus is one type of equipment that uses optical sensors. In an ion implantation apparatus, components such as isolation valves, faradays, and load lock chambers, are monitored by optical sensors. For example, the optical sensors may detect whether the load lock chambers or the or the isolation valves are properly opened or closed. In addition, the optical sensors may be used to determine whether an ion source or a substrate is in a proper position for ion-implantation to take place.
In a “close-type” optical sensor circuit, when an obstruction, or “flag”, prevents a light emitting diode (LED) from transmitting light to a light receiving transistor, the optical sensor circuit outputs a signal with a logic state “low” (i.e., a “low signal”). In contrast, in an “open-type” optical sensor circuit, when a flag prevents the LED from transmitting light to the light receiving transistor, the optical sensor circuit outputs a signal with a logic state “high” (i.e., a “high signal”).
FIG. 1 is a circuit diagram of a conventional “close-type” optical sensor circuit and FIG. 2 is a circuit diagram of a conventional “open-type” optical sensor circuit.
Referring to FIG. 1, the conventional close-type optical sensor circuit comprises an optical sensor 10, a position sensing driver 12, and a LED “LED1”. The close-type optical sensor circuit further comprises a first resistor R1 and a second resistor R2 connected to optical sensor 10.
Optical sensor 10 comprises a LED D1 and a light receiving transistor TR1 that is turned on in response to light emitted from LED D1. A flag “FLAG” is inserted or input between LED D1 and light receiving transistor TR1 to prevent the light emitted from LED D1 from turning on light receiving transistor TR1.
Position sensing driver 12 comprises a transistor 12 having a base connected to an emitter of light receiving transistor TR1, a collector connected to an output of LED “LED1”, and an emitter connected to an output of the close-type optical sensor circuit.
The operation of the close-type optical sensor circuit is as follows. Where flag “FLAG” is not interposed between LED D1 and light receiving transistor T1, the emitter of light receiving transistor T1 assumes logic state “high”, causing transistor Q1 to turn on. Accordingly, current flows through LED “LED1”, causing it to turn on, and as a result, the emitter of transistor Q1 assumes logic state “high”. In contrast, where flag “FLAG” is interposed between LED D1 and light receiving transistor T1, the emitter of light receiving transistor T1 assumes logic state “low”, causing transistor Q1 to turn off. Accordingly, no current flows through LED “LED1”, and as a result, the emitter of transistor Q1 assumes logic state “low”.
The operation of the close-type optical sensor circuit is illustrated by Table 1 below.
TABLE 1FLAG POSITIONTR1Q1LED1Q1 EMITTERFLAG INOFFOFFOFFLOWFLAG OUTONONONHIGH
Referring now to FIG. 2, the open-type optical sensor circuit comprises an optical sensor 20, a position sensing driver 22, a LED “LED2”, and first and second resistors R1 and R12. Optical sensor 20 comprises a LED “D2” and a light receiving transistor TR2 that is turned on in response to light emitted by LED D2. A flag “FLAG” is inserted or input between LED D2 and light receiving transistor TR2 to prevent the light emitted from LED D2 from turning on light receiving transistor TR2. Position sensing driver 22 comprises a transistor Q2 having a base connected to a collector of light receiving transistor TR2, a collector connected to an output of LED “LED2”, and an emitter connected to an output of the open-type optical sensor.
The operation of the open-type optical sensor circuit is as follows. Where flag “FLAG” is not interposed between LED D2 and light receiving transistor T2, the collector of light receiving transistor T2 assumes logic state “low”, causing transistor Q2 to turn off. Accordingly, no current flows through LED “LED2”, and as a result, the emitter of transistor Q2 assumes logic state “low”. In contrast, where flag “FLAG” is interposed between LED D2 and light receiving transistor T2, the collector of light receiving transistor T2 assumes logic state “high”, causing transistor Q1 to turn on. Accordingly, current flows through LED “LED2”, thus turning it on, and as a result, the emitter of transistor Q2 assumes logic state “high”.
The operation of the close-type optical sensor circuit is illustrated by Table 2 below.
TABLE 2FLAG POSITIONTR2Q2LED2Q2 EMITTERFLAG INOFFONONHIGHFLAG OUTONOFFOFFLOW
In the description above, the close-type optical sensor circuit outputs a high signal when no flag is input to optical sensor 10, and the open-type optical sensor circuit outputs a low signal when no flag is input to optical sensor 20. Conversely, where a flag is input to optical sensor 10, the close-type optical sensor circuit outputs a low signal and where a flag is input to optical sensor 20, the open-type optical sensor circuit outputs a high signal.
The output of the closed or open type optical sensor generally provides an indication of the state of some component in a semiconductor manufacturing device. For example, the output may represent whether a door in the device is open or closed. The optical sensor typically detects the state of the component by the presence or absence of the flag.
The optical sensor circuits described above are commonly employed in semiconductor manufacturing equipment. For example, in a semiconductor manufacturing apparatus comprising a processing chamber and a plurality of load lock chambers connected to the process chamber, optical sensor circuits may be used to determine whether the load-lock chambers are properly closed or whether an air bearing in the processing chamber is properly oriented.
Where a close-type or open-type optical sensor circuit is used in the load lock chambers of a semiconductor manufacturing apparatus, malfunctions in one optical sensor circuit can be addressed without interrupting semiconductor manufacturing processes in the processing chamber. This can be accomplished, for example, by removing the malfunctioning optical sensor circuit from its respective load lock chamber and using a different load lock chamber to perform process steps. However, where a close-type or open-type optical sensor circuit is used in the processing chamber, malfunctions in the optical sensor circuit cannot be addressed without interrupting semiconductor manufacturing processes performed therein.